GB2277908A

GB2277908A - Vehicle air-bag arrangement

Info

Publication number: GB2277908A
Application number: GB9315628A
Authority: GB
Inventors: Martin Lindstrom; Stefan Nordin
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 1993-05-11
Filing date: 1993-07-28
Publication date: 1994-11-16
Anticipated expiration: 2013-07-28
Also published as: GB9309638D0; GB2277908B; GB9315628D0

Abstract

An air-bag 3 is mounted beneath a laminated instrument panel 10. The laminate comprises a relatively stiff carrier layer 7 formed of polypropylene or other cheap plastic material, to which is bonded a layer 8 of foamed plastic. The outer foil or skin (9) is formed of thermoplastic elastomer, such as thermoplastic olefin. A cover 12 between the bag and the foamed layer has a line 15 of mechanical weakness which cleaves when the bag inflates to provide doors 16, 17 which hinge outwardly. The choice of materials for the dashboard ensures that the laminate retains its integrity on deployment of the doors, and the arrangement avoids the need for tear lines on the outside of the instrument panel. In an alternative arrangement (Fig 3) the line of mechanical weakness is provided in the carrier layer. <IMAGE>

Description

DESCRIPTION OF INVENTION "INPROVEMENTS IN OR RELATING TO A DASHBOARD ARRANGENENT" THE PRESENT INVENTION relates to a dashboard arrangement and more particularly relates to an dashboard arrangement for use in a motor vehicle.

It has been proposed to provide an air-bag mounted in the instrument panel or dashboard of a motor vehicle, the air-bag being adapted to be inflated in the event that an accident should arise, the air-bag thus providing protection for a passenger travelling in the motor vehicle.

Attempts have been made to make the air-bag as inconspicuous as possible.

EP-A-0465,869 discloses an air-bag arrangement in which the air-bag, in the uninflated form, is retained in position beneath an instrument panel. The instrument panel is provided with a cover formed of a laminate, the laminate consisting of an outer skin, a foam material and an inner retainer layer. A concealed panel is defined immediately above the air-bag by "V"-sectioned grooves or lines of mechanical weakness formed in the underside of the outer skin and formed in the retainer layer. When the air-bag is activated pressure is applied to the under-surface of this concealed panel. In the region of the "V"-sectioned grooves, the material breaks and the entire concealed panel thus becomes separated from the rest of the dashboard assembly, permitting the bag to inflate.

The prior art arrangement described above has two disadvantages. Although the panel is substantially concealed, because there is a "V"-groove or line of mechanical weakness formed in the under-surface of the outer skin of the dashboard assembly, the position of the panel is, in actual fact, visible. A second disadvantage is that on activation of the air-bag the entire concealed panel becomes separated from the rest of the dashboard and may be driven into the vehicle with a substantial velocity. Thus the panel itself may injure a passenger sitting in the vehicle.

A typical outer skin for a prior proposed arrangement is made of polyvinylchloride (PVC), possibly with a core of ABS.

The present invention seeks to provide an improved dashboard arrangement.

According to this invention there is provided a dashboard for a motor vehicle adapted to have an air-bag disposed beneath it, the dashboard comprising an inner relatively stiff carrier layer, a non-brittle foam layer and an outer non-brittle skin or foil layer formed of thermoplastic elastomer, there being means to retain the air-bag in a folded state in an initial position, there being a line of mechanical weakness on an element between the bag and the foam layer to define at least one door, the or each door being adapted to hinge or tilt to an open position in response to pressure from the air-bag when the air-bag is inflated.

Preferably the outer skin or foil layer has no line of mechanical weakness.

The outer skin or foil layer may be made of a thermoplastic elastomer and, preferably, a thermoplastic olefin. The foam layer may be made of polyurethane foam, and the carrier layer may be made of polypropylene or ABS.

In one embodiment of the invention the lines of mechanical weakness are present in the carrier layer.

Preferably the lines of mechanical weakness comprise areas of the carrier layer which are thinner than the remaining parts of the carrier layer.

Conveniently a frame is provided surrounding the area of the carrier layer which defines the areas of mechanical weakness. The frame may be formed integrally with the material of the carrier layer or may comprise a separate frame but made of metal.

Preferably the means retaining the folded bag in the initial position are secured to the carrier layer by means of fastening means which engage the frame.

In an alternative embodiment of the invention the carrier layer has an opening, which is covered by the foam layer and the outer skin or foil layer, the retaining means, which retain the folded bag in an initial position, being provided with a cover, which cover is located between the folded bag and the foam layer, the cover being positioned adjacent the inner surface of the foam layer, the cover being aligned with the opening and the cover being provided with said at least one line of mechanical weakness serving to define at least one door.

Preferably the means to retain the air-bag comprise a housing, the cover being connected to the housing, the housing being connected to support means which in turn are connected to the carrier layer.

Conveniently the housing is provided with a radially outwardly extending flange, the flange defining apertures, securing means passing through the apertures and engaging said support means which in turn are connected to the carrier layer.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which: FIGURE 1 is a sectional view of a dashboard arrangement in accordance with the invention illustrating the components in an initial condition and showing, in phantom, the position of some of the components in a final position, FIGURE 2 is a figure corresponding to Figure 1 illustrating an alternative embodiment of the invention, FIGURE 3 is a sectional view through a modified embodiment of the invention, FIGURE 4 is a perspective view of part of the carrier layer of the embodiment of Figure 3, and FIGURE 5 is a diagrammatic view illustrating the embodiment of Figure 3 and 4 when in use.

At the outset it is to be clearly understood that these drawings are not to scale, with the thicknesses of the various layers in the laminate being greatly exaggerated as compared with the size of the gas generator.

Referring to Figure 1 of the drawings a dashboard arrangement comprises a housing 1 of a substantially conventional design which contains a gas generator 2 and an air-bag 3. The gas-generator 2 is adapted to supply gas to inflate the air-bag 3.

The housing 1 is provided with a radially outwardly extending flange 4, the flange having apertures which receive bolts 5 which engage fixing parts 6 which are bonded or glued to a carrier layer 7 which, together with an intermediate foam layer 8 and an outer "skin" or foil layer 9 form a laminate 1G which comprises part of the instrument panel or dashboard of a motor vehicle.

The carrier layer 7 may have a thickness of 4 mm, the foam layer 8 may have a thickness of 14 mm, and the outer "skin" layer 8 may have a thickness of 1.2 mm.

The housing 1 is mounted on the laminate 10 in alignment with an aperture 11 formed in the carrier layer 7 of the laminate. The aperture 11 is covered by the foam layer 8 and the outer skin or foil layer 9.

The housing 1 is provided with a cover 12 carrying rearwardly directed flanges 13 which are connected by means of bolts or rivets 14 to the open mouth of the housing 1, thus sealing the housing 1 and retaining the air-bag 3 in a folded condition within the housing 1. The cover 12 is formed with a centrally located V-groove or splitline 15, being a line of mechanical weakness.

The splitline 15 effectively defines, in the cover 12, two "doors" 16,17 located to either side of the splitline 15, each "door" being capable of a hinging or tilting movement about the free edge of the door adjacent the rearwardly directed flange 13. The cover 12 is aligned with the aperture 11, and lies adjacent the foam layer 8 exposed by the aperture 11. The cover 12 is located between the air-bag 3 and the foam layer 8.

It is to be noted that the outer-most layer 9 of the laminate 10, which comprises the "skin" or foil layer is not provided with any splitlines at all. It is preferred that this outer "skin" or foil layer is made of a plastic material which is non-brittle within a large temperature range. The preferred material has good tensile properties, and is also tenacious, so that it bonds securely to the underlying foam layer. It is preferred to select a plastic composition which is a thermoplastic elastomer (TPE). Such a material is a thermoplastic material, or a mixture of a thermoplastic material with natural or synthetic rubber, which has elastomeric properties. An appropriate material is a thermoplastic olefin (TPO). In such a case the thermoplastic material is an olefin. Examples are polyethylene or polypropylene mixed with a synthetic rubber such as EPDM or chloroprene. Materials of this type, because they are not brittle, tend to maintain their integrity when the material is broken. Thus pieces of the material do not break away, but the material initially stretches in a resilient manner and then breaks to form two co-herent parts.

The preferred material for the foam layer 8 of the laminate 10 is polyurethane which is also nonbrittle, and is also tenacious, in that it bonds securely to the outer skin or foil layer. However, appropriate TPO foam could also be used. The preferred material for the carrier layer 7 of the laminate 10 is polypropylene.

It is to be appreciated that the polypropylene is a relatively cheap material. Alternatively ABS, another cheap material, may be used. The preferred material for the cover 12 of the air-bag housing 1 is thermoplastic elastomer. Such an elastomer may be of desirable rigidity, while being such that it is easy to form hinge lines and break lines with desirable properties.

On activation of the air-bag arrangement the gas generator 2 generates gas which begins to inflate the air-bag 3. Pressure is applied to the under-surface of the cover 12. The cover 12 breaks along the V-groove or splitline 15 thus forming the two doors 16,17. The doors commence to move outwardly. The arrow 18 indicates the path of movement of the free edge of the door 16 created when the V-groove or splitline 15 actually splits. The door 16 moves to a position shown in phantom 16'. The door 17 moves in a similar manner. As the doors move pressure is applied to the under-surface of the foam layer 8 of the laminate 10 in the region of the splitline 15, and the foam layer and the outer skin or foil layer 9 split in the region of the splitline 15 thus forming two flaps. One flap 19 is illustrated in phantom.

As the doors 16,17 move outwardly to the position shown in phantom, the flaps are driven outwardly.

Because the layers of the laminate which actually split, namely the foam layer 8 and the skin or foil layer 9 are made respectively of polyurethane and thermoplastic olefin, which are non-brittle materials, the laminate breaks evenly, without any parts becoming separated.

Thus the flaps remain coherent and open in a "clean" manner, with no separate elements of the laminate being impelled into the passenger compartment of the motor vehicle.

It is to be appreciated that the arrangement illustrated in Figure 1 therefore has the advantage that there is no line of mechanical weakness on the under-side of the outer skin or foil layer 9 of the laminate 10, which means that the position of the air-bag assembly is totally concealed and is truly invisible. Also, when the air-bag is activated, because the cover of the air-bag housing opens like a pair of doors, pushing back flaps of the laminate material, there is no separate panel of laminate material which can be impelled into the passenger compartment of the motor vehicle.

Additionally, because the laminate is made of appropriate materials, no parts of the laminate become separated from the flaps, and thus no material from the laminate is impelled into the passenger compartment.

Figure 2 illustrates a second embodiment of the invention which is very similar to the first embodiment.

However, in this embodiment the method of fixing the airbag assembly in position is rather different. In the embodiment of Figure 2 a cover 20 for an air-bag assembly is initially mounted in position in an aperture 11 formed in a carrier layer 7 forming together with a foam layer 8 and an outer skin or foil layer 9, a laminate 10 which forms part of the instrument panel or dashboard of a motor vehicle. The layers 7, 8 and 9 may be of the same materials and the same thicknesses as the corresponding layers in the embodiment of Figure 1. The cover 20 comprises a planar portion which is split, by means of a transversely extending "V" -groove or splitline 21 into two "doors" 22,23. The cover is provided, at points around its periphery, with rearwardly directed fingers 24 which pass through apertures provided for that purpose in the carrier layer 7.

The cover carries rearwardly extending flanges 25 which are connected, by means of rivets 26 or the like to forwardly extending flanges 27 provided on an element 28 carried by the chassis of the motor vehicle.

The element 28 has affixed to it flanges 29 which project from a housing 30 containing a gas generator associated with an air-bag 31, the air-bag 31 itself being associated with a transport fixing 32.

The flanges 29 are connected to the element 28 by means of rivets 33 or the like.

It is to be appreciated that in utilising the embodiment of Figure 2 the motor vehicle may be manufactured with the element 28 and the cover 20 in position, and, as a final step in the manufacturing process, the air-bag housing 30 with the air-bag 31 and the associated transport fixing 32 may be moved to the position illustrated in Figure 2, with the flanges 29 then being secured in position by means of the rivets 33.

This minimises any risk of the air-bag inflating unintentionally during manufacture of the motor vehicle.

The embodiment of Figure 2 will operate, when the air-bag is inflated, in the same way as the embodiment of Figure 1.

Figures 3 to 5 illustrate a further modified embodiment of the invention, and like reference numerals are used for like parts which will not be re-described.

In the embodiment of Figures 3 to 5, the gas generator is not provided with a separate cover.

Instead, the carrier layer 7 is provided with lines of mechanical weakness 40 which may have the configuration of "H" so as to define two "doors" 41,42.

The lines of mechanical weakness 40 may be in the form of cuts extending right the way through the carrier layer 7 or may preferably be in the form of regions where the carrier layer is made to be very thin, but not actually perforated. This is preferred since then, when the foam layer 8 is moulded in position adjacent the carrier layer 7 none of the foam will pass through the lines of mechanical weakness 40.

The region defining the "doors" 41,42 may be surrounded by a frame 43 which may be formed either by a thickened part of the carrier layer 7 or preferably, by a separate metal insert.

The bolts 5 passing through the flanges 4 of the air-bag housing 1 pass through the frame 43 and are connected to appropriate nuts 44.

When the air-bag is activated, as shown in Figure 5, the doors defined by the lines of mechanical weakness in the carrier layer will open.

The carrier layer 7 need only be fabricated from a relatively cheap material such as ABS or polypropylene.

When the air-bag is activated, as illustrated in Figure 5, the air-bag itself, 3, will enlarge in size, thus tending to open the doors 41,42. The carrier layer 7, being made of a relatively cheap material, will tend to split at the hinge line, and the foam layer 8 will stretch at the hinge line, to provide the necessary hinging action. Consequently a gap 45 appears in the carrier layer 7 in the region of the hinge line.

The outermost layer 9, being an elastomeric material, simply bends with a hinging action. If the foam layer 8 is made of TPO, it also bends with a hinge action.

Because the carrier layer 7 is firmly bonded to the foam layer 8, none of the carrier layer breaks off, and also, because the outer skin or foil layer 9 is a thermoplastic elastomer, it bends readily to form an acceptable hinge.

Claims

CLAIMS:

1. A dashboard for a motor vehicle adapted to have an air-bag disposed beneath it, the dashboard comprising an inner relatively stiff carrier layer, a non-brittle foam layer and an outer non-brittle skin or foil layer formed of thermoplastic elastomer, there being means to retain the air-bag in a folded state in an initial position, there being a line of mechanical weakness on an element between the bag and the foam layer to define at least one door, the or each door being adapted to hinge or tilt to an open position in response to pressure from the air-bag when the air-bag is inflated.

2. A dashboard according to Claim 1 wherein the outer skin or foil layer has no line of mechanical weakness.

3. A dashboard according to Claim 1 or Claim 2 wherein the outer skin or foil layer is made of thermoplastic elastomer.

4. A dashboard according to Claim 3 in which the outer skin or foil layer is made of thermoplastic olefin.

5. A dashboard according to any one of the preceding Claims wherein the foam layer is made of polyurethane foam.

6. A dashboard according to any one of the preceding Claims wherein the carrier layer is made Cr polypropylene.

7. A dashboard according to any one of the preceding Claims wherein the carrier layer is made of ABS.

8. A dashboard according to any one of the preceding Claims wherein the lines of mechanical weakness are present in the carrier layer.

9. A dashboard according to Claim 8 wherein the lines of mechanical weakness comprise areas of the carrier layer which are thinner than the remaining parts of the carrier layer.

10. A dashboard according to Claim 8 or 9 or wherein a frame is provided surrounding the area of the carrier layer which defines the areas of mechanical weakness.

11. A dashboard arrangement according to Claim 10 wherein the frame is formed integrally with the material of the carrier layer.

12. A dashboard according to Claim 10 wherein the frame comprises a separate frame made of metal.

13. A dashboard according to any one of Claims 10 to 12 wherein the means retaining the folded bag in the initial position are secured to the carrier layer by means of fastening means which engage the frame.

14. A dashboard according to any one of Claims 1 to 7 wherein the carrier layer has an opening, which is covered by the foam layer and the outer skin or foil layer, the retaining means, which retain the folded bag in an initial position, being provided with a cover, which cover is located between the folded bag and the foam layer, the cover being positioned adjacent the inner surface of the foam layer, the cover being aligned with the opening and the cover being provided with said at least one line of mechanical weakness serving to define at least one door.

15. A dashboard according to any one of Claims 1 to 14 wherein the means to retain the air-bag comprise a housing, the cover being connected to the housing, the housing being connected to support means which in turn are connected to the carrier layer.

16. A dashboard according to Claim 15 wherein the housing is provided with a radially outwardly extending flange, the flange defining apertures, securing means passing through the apertures and engaging said support means which in turn are connected to the carrier layer.

17. A dashboard substantially as herein described with reference to and as shown in Figure 1 of the accompanying drawings.

18. A dashboard substantially as herein described with reference to and as shown in Figure 2 of the accompanying drawings.

19. A dashboard substantially as herein described with reference to and as shown in Figures 3 to 5 of the accompanying drawings.

20. Any novel feature or combination of features disclosed herein.